This invention relates to a method for processing a light-sensitive silver halide color photographic material, particularly to a processing method in which stain generation occurring in the bleaching step is suppressed.
Diequivalent couplers which can generally improve much of the image quality of a light-sensitive silver halide color photographic material has been employed in many light-sensitive color photographic materials in recent years. However, as well known in the art, when said diequivalent coupler is processed in a processing bath having a bleaching ability in which a color developing solution is mixed therein, color fog called as stain is liable to be formed, whereby a serious problem which is undesirable in color reproduction of photographic image may be caused.
Also, in the bleaching step, an aminopolycarboxylic acid iron complex is primarily employed as the bleaching agent, and when processing is conducted with a bleaching solution or a bleach-fixing solution employing an ethylenediaminetetraacetic acid iron (III) complex, which is the most common of said aminopolycarboxylic acid iron complexes in this field of the art, the above stain is known to be readily generated. It is also known that such a phenomenon occurs frequently particularly when direct bleaching processing or bleach-fixing processing is conducted after color developing and processing is conducted during the season when the amount of the light-sensitive silver halide color photographic materials to be processed is small.
As a means for prevention of such a phenomenon, it has been proposed to modify the solution by addition of a sulfite when the amount of the light-sensitive silver halide color photographic materials to be processed is reduced.
Reduction in amount of the light-sensitive silver halide color photographic materials to be processed often occurs at the weekend during one week, and during the year, in the periods of from the end of January to March and from July to September. During these periods, depression may occur even to 1/4 to 1/5 of the amount at the period of maximum processing. Such an extreme reduction in processing amount is characterized by lowering in frequency of renewal of a tank solution very susceptible to air oxidation such as a bleach-fixing solution with fresh supplementing solution to result in deterioration of the processing solution, whereby stain is liable to be generated. In such a case, there also ensues the economical problem that the tank solution must but be renewed with a fresh one.
On the other hand, when carrying out direct bleach-fixing processing after color developing, the color developer is brought into the direct bleach-fixing solution by conveying of the photographic light-sensitive material, and therefore the developing agent is oxidized in the bleach-fixing solution, thereby causing readily color formed stain. Particularly, this tendency becomes intensified when the renewal frequency is lowered with reduction in amount of processing.
Further, in these days, for the purpose of prevention of environmental pollution or conservation of resources, the low supplementing processing is under progress, in which processing is conducted with an amount as small as possible of a processing solution supplemented per unit area of the light-sensitive silver halide color photographic material to be processed. According to such a processing, particularly the proportion of the color developer entrained into the bleach-fixing solution as mentioned above will be increased to give rise readily to generation of stain and also lower the bleach-fixing speed.
To cope with these problems, for the purpose of preventing so far as possible generation of stain and enhancing storability of the solution on reduction of processing amount, it has been recommended and practiced in part to add a certain quantity of a sulfite or a sulfite releasing compound such as sulfurous acid formaldehyde adduct.
Also, for prevention only of stain, it is also well known in the art and practiced to carry out processing on the acidic side by lowering the pH value of the bleach-fixing solution, whereby stain can be suppressed to a great extent. However, according to such a method, even if generation of stain itself may be prevented, the amount of the reducing agent becomes too much at the initial period of the week when the processing amount is great, to result in reduction of the bleaching agent of an ethylenediaminetetraacetic acid iron (III) complex (EDTA Fe(III) salt) to form an ethylenediaminetetraacetic acid iron (II) complex (EDTA Fe(II) salt), whereby there is involved the problem of causing a serious drawback of poor color restoration due to leuco formation of the cyan dye. On the other hand, lowering the pH accelerates hydrogen addition (protonation) to the above cyan dye with the EDTA Fe(II) salt which is the reduced product formed by the bleaching reaction of silver, thereby also increasing disadvantageously poor color restoration. Thus, generally speaking, with a bleaching solution of the prior art employing EDTA Fe(III), salt, it has been practically impossible to make the pH of the bleach-fixing solution 6.5 or less, even the pH of the bleaching solution 5.9 or less.
On the other hand, as to the upper limit of the pH of a bleaching solution or a bleach-fixing solution, it cannot generally be made 7.5 or higher, because higher pH will cause markedly generation of the above stain. Accordingly, although these processing solutions are prescribed generally as useful at pH 2.0 to 8.0, they are actually managed at a very narrow range of pH 6.0 to 7.5, and it is further required to manage more precisely the processing solution such as for correction of the solution by addition of a sulfite corresponding to the supplementing amount, measurement of oxidation-reduction potential or the processing amount.
Further, in these processing solutions, management by air oxidation (aeration) requires more precise system control.
Generally speaking, in bleaching solutions or bleach-fixing solutions, oxidizing agents such as EDTA Fe(III) salts are known to cause undesirable problems of being reduced through (1) the bleaching reaction with silver, (2) the redox reduction with a sulfite, (3) the redox reduction by entrainment of a reducing agent (developing agent, etc.) in the developer, to form an EDTA Fe(II) salt which reduces the dye. Accordingly, it is necessary to oxidize such an EDTA Fe(II) salt to be returned to an EDTA Fe(III) salt, and it is generally required to practice air oxidation constantly or intermittently by the method of passing bubbles of air through the solution which is called as the abovementioned aeration. However, while this method is a very simple and effective method for improvement of bad color restoration, the so called overaeration, in which aeration is excessively effected, tends to occur, under which state generation of stain will occur markedly mentioned above. For this reason, until now, there is employed the management system where processing is conducted by controlling the air quantity while measuring constantly the redox potential at a level where the reduced product EDTA Fe(II) remains slightly. Thus, management has been very complicated.